Spark plug



'June 26, 1928. 1,674,977

W. MCELROY SPARK PLUG Filed May 29, 1926 j! II 9c] a 2 'INVENTOR.

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Patented June 26, 1928.

UNITED STATES PATENT OFFICE.

"WILLIAM MCELROY, 0F BROOKLYN. NEW YORK, ASSIGNOR OF ONE-HALF TO MICHAEL LUDGIN, OF BROOKLYN, NEW YORK.

SPARK PLUG.

Application filed May 29,

This invention is a spark plug. The object ot' the invention is to provide a plug olrelatively simple construction, but capable ct high cttieiency through long periods o'tuse. he invention is more particularly directed to the electrodes of the plug and generally speaking, in the provision ot' electrodes which are capable of adjustinznt in such manner as to present difierent POltlJltb ot the electrodes at the point of sparking. so that when one portion of each electrode becomes pitted or badly disintegrated, another portion of such electrode may be presented at the gap.

1 have discovered that the foregoing objects may be efiiciently and economically obtained by making the electrodes in the form of spiral springs and so mounting the springs that they are capable of movement either in the nature ot bodily movement or of distending operation to present ditl'erent portions of the springs at the gap.

1 am aware that it has been heretofore proposed to mount; coil springs of wire upon the electrodes ot a conventional plug in such manner that the inherent resiliency ot the coil springs used in this connection will grip the conventional electrodes and be held in place by such frictional engagement. Ex periencc has shown. however, that when a coil spring is subjected to the rapid continued variation in temperatures to which the electrode of a plug is subjected, springs thus associated with the electrode will not only lose their resilienoy but will appreciably expand and drop on into the motor, thereby constituting a serious hazard to the inecluinism.

The present invention is not to be confused with this prior practice, since the electrodes. per se. are in the form of coils of wire and are not separate and independent coil springs associated with an electrode.

in the preferred manner of carrying out the present invention, the central electrode is in the form of a rod which extends through the porcelain with a binding post associated with the upper end of the rod and the lower end ot' the rod formed into a series of coils or convolutions. The grounded electrode is mounted upon a suitable guide. in the form of a yoke. both ends of which are anchored to the shell of the plug and the coil which constitutes the grounded electrode 1926. Serial No. 112,467.

embraces this yoke and is either mounted for tree longitudinal movement on the yoke or is anchored in such manner that movement of the coil to present. ditl'erent portions thereof at the cap is manually obtained by stretching the coil. As thus specified, there is no possibility of the coils becoming disengaged from the plug and the desired adjustments may be made from time to time as occasion may require in a simple and expeditious manner.

Features of the invention. other than those specified, will be apparent from the hereinat'tcr detailed description and claims, when read in conjunction with the accompanying drawings.

The accompanying drawings illustrate dittercnt practical embodiments of the invention, but the constructions therein shown are to be understood as illustrative. only, and not as defining the limits of the invention.

Figure l is a vertical central section of a spark plug embodying the present invention.

Figure 2 is a bottom plan view of the plug shown in Figure 1.

Figure 3 is a view similar to Figure 52, but illustrating a modified form of the invention; and,

Figure at a side elevation, partly in section of a moditied form of central electrode.

The plug shown in the drawings embodies the usual metal shell 1 having a threaded shank 2 and interiorly of which is mounted a porcelain 3 held rigidly in position by a jainb nut 4.

In the construction shown in Figures 1 to 3. the central electrode is in the form of a rod or wire 5 which extends longitudinally through the porcelain and is provided at its lower end with a series of coils or convolutions. The coil paution of the wire 5 extends into the lower end of the porcelain, which is chambered as shown at T to receive it.

The purpose of this construction is to permit the coil portion of the rod to be properly supported against lateral movement which might seriously vary the dimension of the gap of the plug. The upper end of the rod or wire 5 is bent over the upper portion of the porcelain as shown at 8 and a metalcap 9 is spun over the upper portion of the porcelain so as to make good electrical contact with and cover the upper end of the rod 5. This metal cap carries a suitable binding post 10 with which is associated conventional nuts 11.

In the construction of Fiat:

g re 4, the coil 6, which constitutes the central electrode, is made separate from that portion 5* ol the stem which extends through the porcelain, but attached thereto by carrying the upper end of the coil through a perforation in the rod and then bending the wire of the coil as shown at 12 to permanently lock the parts together. The rod 5 is shown as extrading downwardly into the coil 6 for a dis tance tor the purpose of steadying the coil against lateral mmcment. but it the upper portion of the coil is housed within a pocket 7 in the porcelain corresponding to the pocket T of Figure 1. the rod need not extend downwardly as shown. but may tern1inate just below the perforation where the end of the coil is securtal to the rod. The upper end of the rod is proyidcd with the usual nuts for securing the ignition lead to the plug.

The grounded electrode may be constructed as shown in either Figures 2 or :5. Ii Figure 2 a yoke It, preferably of heavy wire, is secured at both of its endsto the lower end of the shank 2. About this \'0lil. the electrode 15 is coiled. One end of the coil is left free, while the other end is anchored to the shell as show u at ll).

In Figure 3. the structure is in many h spects similar to that of Figure :2. except that the groumled electrode 15 is unattached and is adapted l'or free sliding movement longitudinally of the yoke.

IVhen a plug is provided with electrodes of the character described. it will be apparent that that portion of the central electrode which cooperates with the grounded electrode at the gap may be varied as desired. Initially, the central electrode is in the form of a close coil, and the lower end thereof is juxtaposed with the grounded electrode. If such lower end becomes badly pitted or burned away, the coil may be slightly (ll tended or elongated to present a new portion thereof at the gap and this operation may be repeated from time to time as circumstances require to maintain a proper operating condition of the central electrode.

In practice, this elongation of the coil may be expeditiously accomplished. since the coil does not possess any appreciable inherent resiliency and will. in tact, stay in substantially the position to which it has been adjusted. The same manner of adjustment is true with respect to the construction of Figure 2, it being manifest that the coil may be shifted manually longitudinally ol the yoke to present ditierent operative portions of its length at the gap. In Figure 3, however.

the vibration of the or will serve to constantly ary the position of the coil on the yoke. so as to bring about an automatic constant change at the gap.

By employing coils in the manner in which I have described. the vibration of the engine will cause an almost constant move-- ment ol the coils. This movement is in practice slight. so slight in hurt that it would not be perceptible to the eye. NevertlltlUt-il ihcre is a movement ot' the parts which inmres cleanliness of the electrodes since by virtue of such moremcnt, the deposit ol' extraneous matter such as carbon is rendered impossible.

It is to be understood, h wevrr, that the moycment to which I have referred will not seriously interfere with the maintenamrc ot the desired gap nor will such movcinvnl preclude proper functioning of the plug. Nevertheh as the parts will be kept clean and opcratiic through long period. The invention is of simple construction. economical to manufacture and highly ctlicient in operation. 5 The drawings show the invention in its prctcrred practical forms, but the invention is to be understood as l'ully commensurate wiih the appended claims.

l'laving thus fully described the invention, what I claim as new and desire to secure by lictteri latcnt is:

l. A spark plug embodying a shell. a grounded electrode at the bottom of said shell. a porcelain provided in its lowcr end with a pocket and mounted on the shell. a central electrode extending through the pol' cclain and with an integral tormed coil of wire extending from within the pocket to :1V point adjacent to and laterally ot the grounded electrode and forming therewith the gap of the plug. said coil being of easily bendable wire, initially formed with closely spaced convolutions adapted to be manually elongated from time to time to present different convolutions ol' the coil at the gap.

2. A, spar-l; plug embodying a :-llt%ll. a porcelain associatcd therewith. an in.-.ulated electrode extending through the porcelain. a substantially U shaped yoke. both arms of which are anchor-rd in the shell and the intermediate part of which is longit dinally curved to extend around the side oi the insulated electrode. and a grounded electrode in the form of a coil loosely embracing the laterally curved part of said yoke and mounted to freely shiit longitudinally thereof.

In testimony whercol'. 'rrnmn McEhnoY signed his name to this specification 28th day of May, i926.

'ILLIAM MCELRUY.

has this 

